Brief Description: Nautiluses are marine natatory organisms and can live in various depths due to their shell?s construction (they are molluscs-cephalopods). They appeared in the Upper Cambrian, live until today and are only represented by one genus, Nautilus, with 6 species. This species is the only one of the cephalopods that bears a shell. Its shell has about 20 cm diameter, is flat and spirally coiled and bears simple decoration on the external surface, consisting of almost radial coloured bands that bear irregular or symmetrical on both sides, brown-orange stripes. The animal's body consists of: a) the main body, which is surrounded by the radula and consists of the radula-chamber and the bowels, and b) the cephalopod that bears 38 tentacles that surround the mouth. The mouth bears keratinoid jaws that look like a bird?s beak and constitute the snout. The snout is calcified and fossilized, like the nautilus shell. From the end of the Upper Cambrian, Nautiluses show an explosive radial development and in the beginning of the Ordovician Period, several fossilized genera appear. Up to this day, 6 Orders have been identified, five of which have become extinct. The last order (Nautilida) which exists even today appeared in the fossils archive in the beginning of the Devonian Period. In the geological formations of Greece, fossilized Nautiloids can be found together with other Cephalopods and Ammonoidea. 
Bibliography: Γεωργιάδου-Δικαιούλια, Ε., Συμεωνίδης, Ν., Θεοδώρου, Γ. (2003) Παλαιο-ντολογία (μέρος Β?), Εκδόσεις Γ. Γκελμπέση, Αθήνα.